It was already nearly as hot as it had been the day before; but clouds were beginning to come up from the West. It looked likely to turn to rain. The hobbits scrambled down a steep green bank and plunged into the thick trees below. Their course had been chosen to leave Woodhall to their left, and to cut slanting through the woods that clustered along the eastern side of the hills, until they reached the flats beyond. Then they could make straight for the Ferry over country that was open, except for a few ditches and fences. Frodo reckoned they had eighteen miles to go in a straight line.
He soon found that the thicket was closer and more tangled than it had appeared. There were no paths in the undergrowth, and they did not get on very fast. When they had struggled to the bottom of the bank, they found a stream running down from the hills behind in a deeply dug bed with steep slippery sides overhung with brambles. Most inconveniently it cut across the line they had chosen. They could not jump over it, nor indeed get across it at all without getting wet, scratched, and muddy. They halted, wondering what to do. ‘First check!’ said Pippin, smiling grimly.
Sam Gamgee looked back. Through an opening in the trees he caught a glimpse of the top of the green bank from which they had climbed down.
‘Look!’ he said, clutching Frodo by the arm. They all looked, and on the edge high above them they saw against the sky a horse standing. Beside it stooped a black figure.
[FOTR, Ch. 4: A Short Cut to Mushrooms]

Pippin had vanished. The crack, by which he had laid himself, had closed together, so that not a chink could be seen. Merry was trapped: another crack had closed about his waist; his legs lay outside, but the rest of him was inside a dark opening, the edges of which gripped like a pair of pincers.

Even as Frodo spoke he felt a great malice bent upon him, and a deadly regard considering him. Not far down the tunnel, between them and the opening where they had reeled and stumbled, he was aware of eyes growing visible, two great clusters of many-windowed eyes – the coming menace was unmasked at last. The radiance of the star-glass was broken and thrown back from their thousand facets, but behind the glitter a pale deadly fire began steadily to glow within, a flame kindled in some deep pit of evil thought. Monstrous and abominable eyes they were, bestial and yet filled with purpose and with hideous delight, gloating over their prey trapped beyond all hope of escape.

As they prepared for sleep in the inn at Bree, darkness lay on Buckland; a mist strayed in the dells and along the river-bank. The house at Crickhollow stood silent. Fatty Bolger opened the door cautiously and peered out. A feeling of fear had been growing on him all day, and he was unable to rest or go to bed: there was a brooding threat in the breathless night-air. As he stared out into the gloom, a black shadow moved under the trees; the gate seemed to open of its own accord and close again without a sound. Terror seized him. He shrank back, and for a moment he stood trembling in the hall. Then he shut and locked the door.

The night deepened. There came the soft sound of horses led with stealth along the lane. Outside the gate they stopped, and three black figures entered, like shades of night creeping across the ground. One went to the door, one to the corner of the house on either side; and there they stood, as still as the shadows of stones, while night went slowly on. The house and the quiet trees seemed to be waiting breathlessly.

There was a faint stir in the leaves, and a cock crowed far away. The cold hour before dawn was passing. The figure by the door moved. In the dark without moon or stars a drawn blade gleamed, as if a chill light had been unsheathed.

[FOTR, Ch. 11: A Knife in the Dark]